Anomalous field effect and glassy behaviour in granular aluminium thin films: electron glass?

TL;DR

This study investigates non-equilibrium conductance phenomena in insulating granular aluminium thin films, revealing anomalous field effects and slow relaxation similar to other electron glass systems, and discusses possible electronic or dielectric origins.

Contribution

It provides experimental insights into anomalous field effects in granular aluminium films and compares two potential mechanisms, advancing understanding of electron glass behavior in disordered systems.

Findings

Observation of anomalous field effect and slow relaxation in granular aluminium.

Phenomenology similar to indium oxide electron glasses.

Discussion of dielectric polarization versus electronic Coulomb glass mechanisms.

Abstract

We present a study of non-equilibrium phenomena observed in the electrical conductance of insulating granular aluminium thin films. An anomalous field effect and its slow relaxation are studied in some detail. The phenomenology is very similar to the one already observed in indium oxide. The origin of the phenomena is discussed. In granular systems, the present experiments can naturally be interpreted along two different lines. One relies on a slow polarisation in the dielectric surrounding the metallic islands. The other one relies on a purely electronic mechanism: the formation of an electron Coulomb glass in the granular metal. More selective experiments and/or quantitative predictions about the Coulomb glass properties are still needed to definitely distinguish between the two scenarii.